1. Field of the Invention
The present invention relates to a printing technique of ejecting a plurality of inks on a printing medium to print an image.
2. Description of the Related Art
Color printers that eject multiple different color inks from a print head have widely been used as the output device of the computer to print computer-processed images in multiple colors and multiple tones. One applicable method for such tone expression selectively forms one among multiple variable-size dots in the area of one pixel on a printing medium.
This tone expression technique records the respective size dots at adequate recording rates to express the various tone values. The dot recording rates of the respective size dots are set in advance to enable adequate allocation of the respective size dots and thereby restrain the potential deterioration of the picture quality, for example, to lower the granularity (the roughness of the resulting image) and the visibility of banding (deterioration of the picture quality by the appearance of streaks).
A quality-enhancing ink for improving the quality of a printed material may be used in such printers as disclosed in, for example, Japanese Patent Laid-Open Gazette No. 2002-144551. The quality-enhancing ink improves the properties like color development, water resistance, and light stability and prevents a variation in gloss to attain the high quality of the printed materials. The quality-enhancing ink is practically transparent. Reduction of the processing time required for generation of the dot data is accordingly more important than reduction of the deterioration of picture quality by adequate allocation of the respective size dots.
The prior art technique, however, does not set the dot recording rate of the dot formed with the quality-enhancing ink from the perspective of reduction of the processing time required for generation of the dot data.